This invention relates to a robot control apparatus for servo-controlling various drive means by calculating, on-line, the torque command of a robot arm on the basis of the motion equation of a manipulator.
Horizontal articulated-type robots of the kind shown in FIG. 4 have recently come into use on factory assembly lines and the like. A robot of this type comprises a post 1, a first arm 2, a second arm 3, a hand 4, a joint shaft 5, a cable 6, a base 11 and covers 22, 32. When the arms and the hand are driven by servomotors (not shown) to grip a workpiece and perform other motions, a torque command for the robot arms is calculated on-line by a microcomputer for servo-control based on a manipulator motion equation, whereby each of the drive means is servo-controlled.
The drive torque of a servomotor used for robot arm drive is determined as a function of the weight of the workpiece gripped by the hand and inertia determined by the length of the arm. However, the torque necessary for motion when the workpiece is being gripped differs from that when the workpiece is not being gripped. Accordingly, the operator provides a control unit with inputs indicative of whether the robot arm is gripping a workpiece, the weight of the workpiece, etc., and the control unit calculates inertia by computing complicated simultaneous equations, thereby commanding a drive torque of the servomotor. Consequently, the operation for commanding the drive torque of the servomotor is troublesome and the processing performed by the control unit is complicated. In order to compute other parameters such as control current during execution of this processing, a considerable high-speed processing capability is required.